This invention relates to latches for vehicle doors, particularly for light passenger and goods vehicles.
Powered locking and powered latching of doors is becoming more favoured, both as part of central locking systems, and to enable more effective weathersealing of doors and greater freedom in styling and design. There are also advantages in providing for power actuated unlatching of doors in terms of dispensing with much of the mechanical linkage and components needed for conventional manual inside and outside door handles, and in providing unitary lock and latch modules of standard form which can be speedily insalled in doors of a wide range of vehicle models and types without special adaptation.
An example of the provision of power closing is described and claimed in our co-pending patent application GB 9710602.5 dated May 23rd 1997, and the present invention may conveniently be combined with that construction if desired.
The object of the invention is to provide improvements in vehicle door latch assemblies, in particular the provision of latches having a power unlatching facility in an economical, effective and reliable form.
According to the invention there is provided a vehicle door latch assembly including a pivotally mounted latch claw having a mouth operatively co-acting with a striker as the door nears its closed position, a latching pawl self-engaging with the claw to hold it in latched condition retaining the door, and unlatching means selectively operable to disengage the latching pawl for opening the door: characterised in that the unlatching means comprises a pawl lifter movable from a position of rest to carry the latching pawl out of engagement with the claw, a power output member movable to engage and displace the pawl lifter from said position of rest, an input member power actuated between first and second positions, clutch means releasably drive connecting the input member to the output member to cause shifting of the latter as the input member moves to its second position, and an overriding element carrying the clutch means into and out of drive connection, said overriding element being operatively coupled to manually operable release means of the door to ensure that manual operation of the pawl lifter is not obstructed by failure or malfunction of power actuation of the input member.
The output member is conveniently a power release lever having an arm positioned for engagement with the pawl lifter and a second arm provided with a drive formation forming a first element of the clutch means.
The input member may be a crank element coupled to an electric or other power actuator for angular movement and carrying a drive formation forming a second element of the clutch means, the pivot of the crank element being carried on the overriding element which is shifted on manual operation of the release means to move the crank element in a direction disengaging said drive formations of the clutch means.